refactoring_rails_err.rb

module MyTransaction
  def save
    Transaction.instance_eval do
      @@save = instance_method(:save)
      remove_method :save
    end
  
    body = "my transaction! + " + super
    
    Transaction.module_eval do
      define_method :save do
        @@save.bind(self).call
      end
    end
    
    return body
  end
end